import java.util.*;

public class JumpingStones {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        

        int n = scanner.nextInt();
        

        int start = scanner.nextInt();
        
        System.out.print("请输入小石子每次最大的跳跃距离：");
        int maxJump = scanner.nextInt();
        
        int[] dp = new int[n + 1];
        Arrays.fill(dp, Integer.MAX_VALUE);
        dp[start] = 0;
        
        for (int i = start; i <= n; i++) {
            if (dp[i] == Integer.MAX_VALUE) {
                continue;
            }
            
            for (int j = 1; j <= maxJump; j++) {
                int pos = i + j;
                if (pos > n) {
                    break;
                }
                
                if (dp[pos] > dp[i] + 1) {
                    dp[pos] = dp[i] + 1;
                }
            }
        }
        
        if (dp[n] == Integer.MAX_VALUE) {
            System.out.println("无法到达终点石板！");
        } else {
            System.out.println("到达终点石板的最少跳跃次数为：" + dp[n]);
        }
    }
}